Field of the Invention
The present invention relates to a piezoelectric ceramics and a method for manufacturing the same.
Description of the Related Art
A piezoelectric body is applied, as a material which is capable of converting electrical energy into mechanical energy, in various fields such as a filter and an actuator. A currently mainstream piezoelectric material is a lead-based perovskite compound containing a main component of lead titanate zirconate (Pb(Zr,Ti)O3). This compound contains the lead (in particular, PbO), and thus it is suspected damage to natural environment and the like. In view of this, an investigation is started to use a non-lead-based piezoelectric ceramics as an alternative material to the lead-based piezoelectric material from a standpoint of the natural environmental consideration.
As the non-lead-based piezoelectric ceramics, a material composed mainly of potassium sodium niobate ((K,Na)NbO3) is known as a material in which piezoelectric characteristics such as electromechanical coupling coefficient and mechanical quality factor are superior.
In a case that the piezoelectric ceramics as described above is produced, the piezoelectric ceramics is required to be sintered for a long period of time (in general, for 2 to 5 hours, for example). However, there is such a problem that difference in composition is occurred because highly-volatile K, Na components evaporate easily. In view of this, in order to complete sintering for a short period of time and to improve productivity, a sintering aid or a sintering additive is added to the piezoelectric ceramics.
For example, Japanese Patent Application laid-open No. 2011-88786 discloses a piezoelectric ceramics in which, as the sintering aid, an oxide containing Cu and Ta or containing Cu and Nb, and a simple perovskite compound represented by the composition formula MTiO3 (in the composition formula, M is Ca or Sr) are blended with respect to a perovskite compound of a non-stoichiometric composition represented by the composition formula (KxNa1-x)y(Nb1-zTaz)O3 (in the composition formula, 0<x≦1, 0<y<1, 0≦z≦0.5). This piezoelectric ceramics has superior piezoelectric characteristics and high productivity.